Modern Warfare 2 Unlimited Ammo Cheat?

There have been a number of reports that the is a cheat in the Xbox 360 Modern Warfare 2 game where your ammo counters are not working correctly. It seems that some players are joining multi-player games and finding that they have no ammo counters, instead all ammo is unlimited.
I haven't noticed this yet when I play Modern Warfare 2.

According to kotaku.com, there is not much to go on, but it seems that it is an exploit in the game that modders have created to have Unlimited Ammo.

Yes there is an unlimited ammo cheat in Modern Warfare 2.
The cheat is only available for some modders, who’ve managed to get access to the game’s data and modified it. The bigger problem is that the cheat is passed on to anyone who’s played with the modder, as it’s saved to your console’s cache. It shouldn’t cause any damage, so don’t worry about that.

There’s no permanent fix as of now – the only solution is to disconnect from Xbox Live and reboot your console.
Some Modern Warfare 2 fans are so mad right now.

I experienced this cheat, and hilarity ensued. Unlimited ammo for ANY weapon, including missiles and grenade launchers. However, it was not "saved on my console's cache". I left the room, and the very next game, the unlimited ammo was gone. You should've seen the accuracy go down! I bet most of those folks saw a decline of two or three percentage points. Suffice to say, it needs to be fixed.